The earlier pictures were taken on my wee compact Canon ixus 970IS, which involved sneaking up on the butterflies. This can be very frustrating when they fly off, but very rewarding when they don't!

Since 2012 I have been using a Panasonic Lumix FZ150, which allows me to zoom in to the butterflies from a couple of metres away.



Thursday, 28 March 2013

Small Tortoiseshell - Aglais urticae

Almost every year the first butterfly I see is a Small Tortoiseshell, Aglais urticae. This year I saw one on the 2nd March, and I thought that it was going to be a good start to the butterfly season, but the weather turned for the worst the next day. Temperatures haven't been much above freezing since, and we have had snow showers for the last 12 days in a row! The forecast doesn't look as though things are going to change for the foreseeable future. At least the weather has given me a chance to sort through some of my old photographs.



The Small Tortoiseshell was once one of the most commonly seen butterflies in the UK. It can be seen almost anywhere in the British Isles at almost any time of the year. Typically there are two broods. The butterflies that we see at this time of year emerged around about September the previous summer. After the adult butterflies emerge they feed up before finding themselves a dry spot, such as a shed or log pile to hibernate. During mild, sunny days over the winter the butterfly may be seen flying around. This can be a little risky, as there is unlikely to be a nectar source available and the butterfly will needlessly be using up energy.

It is more normal for the adults to start appearing in late March, when there are spring flowers available for them to feed on. These butterflies will go on to lay eggs in May, which will turn into the next generation of butterflies around about July. The July adults pair up very quickly and go on to produce the generation that overwinters. So, the summer brood has a lifespan of about three months while the winter brood has a lifespan of about nine months.


Two summers ago, I was walking our dog along a local farm track and I noticed this female Small Tortoiseshell behaving a little strangely. I watched for a while and realised that she was laying eggs on some nettles alongside the track.


It took her over half an hour to lay this batch of eggs.


I kept an eye on the eggs for the next few days. The weather turned cool and wet and it took the eggs eighteen days before they hatched. I am sure that they would not take as long in warmer weather.


The day after they hatched I went away for a few days and on my return there was no sign of the caterpillars. Sadly, I think they must have perished due to the poor weather.

I regularly see Small Tortoiseshell caterpillars on the nettles along that track. They aren't difficult to spot, as after they hatch they build a communal web towards the top of the nettle plant. The butterflies remain as a mass as they move around the nettles leaving a trail of eaten leaves and droppings.


The caterpillars are black with yellow stripes and covered in spines.


When they reach the final instar the caterpillars have more obvious yellow stripes and they become solitary.

I found the following three prints today and scanned them. They were taken in 2001 when I was working as a Countryside Ranger at John Muir Country Park, near Dunbar, Scotland. I have checked my notes and notice that I spotted the freshly hatched caterpillars and 21 days later they turned into chrysalises. It was interesting that most of the chrysalises were a beautiful shimmering gold, but there were a few dark brown ones, too. Most of them were attached to the stems and leaves of the nettles close to where they had been feeding, but others had climbed a close by shed and formed chrysalises under the eaves of the roof.




I noted that after 18 days the adult butterflies eclosed.

I said at the beginning that the Small Tortoiseshell was once a very familiar butterfly here in the UK. Unfortunately its numbers have been declining in recent years. It isn't known for sure what is causing this, but the best theory is that climate change has allowed the parasitic fly, Sturmia bella, to expand its range into the UK. This fly lays its eggs on the nettle leaves that the butterflies are feeding on. The eggs are ingested by the caterpillars and the larva of the flies slowly consume their hosts. It seems that the biggest impact on Small Tortoiseshell numbers has been in southern England and here in Scotland the population is remaining stable.


Hopefully this cold weather will soon come to an end and I'll be seeing Small Tortoiseshells and other butterflies out and about.

18 comments:

  1. Wow, you got into the heart of the matter. That macro close-up of the eggs hatching is awesome. I love the other close-up which is just the green leaves with the eggs. The camera you got is great, I was about to get one the other day too, because mine only zooms up to 16x. The problem with my Calotropis milkweed tree is that it's so huge, that I need my big zoom to get the last of the larvae. Beautiful work. If you continue to document all of this, you can publish a book!

    ReplyDelete
    Replies
    1. Thanks Maria. Those two close-ups were taken with my little Canon compact camera. It is great for that sort of thing. The Panasonic Lumix is great for zooming into more distant butterflies. It has a X24 zoom, that they say goes up to x32, but that is just digitally cropped.

      Delete
  2. A thoroughly absorbing post Nick with lovely photos too. Great to see the eggs so closely. The Small Tortoiseshell seems to have fared fairly well in recent years here although given what dreadful weather we had last year that may have changed. I saw a report, just this week, confirming how badly butterflies in general were affected which I'm sure we were all fearing. I was saddened to only see one Common Blue all year! Best wishes, Jan.

    ReplyDelete
    Replies
    1. Songbird. The weather can only be better this year, surely! I think that much depended last on when the rain hit. Up here it was the first generation of whites that suffered. The Common Blue didn't do too badly, as there was a bit of a dryer spell when they were around. What I think will have done the most damage is the flooding. All of the area where the Orange Tips laid their eggs bu the local river was flooded in May. We then had further bad flooding in November which will have hit the Meadow Browns and Ringlets. It will be interesting to see how the numbers are this year. I'm keeping my fingers crossed.

      Delete
  3. Nick, These are wonderful photos of your observations! Beautiful portraits of a gorgeous butterfly. It is so exciting to discover so many eggs and to be able to observe and record as you have. Thanks tons for sharing these. Great to connect with you too. Carol

    ReplyDelete
    Replies
    1. Hi Carol, I am glad that you found them interesting. I find the whole life-cycle fascinating.

      Delete
  4. Good work, Nick. This post is an amazing documentation of the life cycle of this gorgeous butterfly. Its worthy of Nat Geo publication. The first photo showcases its rich colour in all its splendour. The freshly-laid green eggs are lovely to look at but the knot of wriggly black caterpillars are quite disturbing to the senses.

    ReplyDelete
    Replies
    1. Thanks Stiletto. It's funny how one caterpillar can be endearing, but a mass of them is quite repulsive. It was funny as I found that group of Small Tortoiseshell caterpillars when I was walking our dog with my wife. I was quite excited, but she said it was a repulsive, writhing mass!

      Delete
  5. Great post with lovely photos of a common but beautiful butterfly!
    Well done, congrats!!

    ReplyDelete
  6. Hi Nick, I just reread this post and find it so interesting. I love connecting around the globe through a love of butterflies. We do get the Milbert's Tortoiseshell here in Western Massachusetts but I have yet to see it. I am inspired by your sightings and hope to see one of these beauties this year. They are rare to uncommon here. The Milbert's too prefer the nettles. Ours overwinter as adults and perhaps yours do too . . . sap may help them get through till nectar sources appear. It has been very cold here too. Last year we were two weeks early and this year it is well two weeks late. Nature is very fickled and with climate change who knows. Good luck with your sightings! Carol

    ReplyDelete
    Replies
    1. Thanks for your comments Carol. Yes, it is great being able to hear from enthusiasts around the world. I have seen pictures of Milbert's Tortoiseshells and they are really beautiful. I think I prefer them to the ones we get here, but maybe it is just because they are different!! It is interesting how your weather is mirroring ours. Last year everything kicked off in early March. This year everything is very late and still there is very little sign of plants growing or insects appearing. Hopefully it will all start soon!

      Delete
  7. Hello Nick
    This is my second visit to your excellent post, but I didn't have time to comment the first time. Gosh,it's just brilliant how much you know and have documented.Your macos are so interesting,and your photos of the beautiful Tortoiseshell butterfly are just lovely.I wish the Tortoiseshell would appear more often in my garden, as I only saw one last year, and not one so far this year, but then the weather has been unseasonably cold and rainy here in Portugal.
    Regards
    Sonjia

    ReplyDelete
    Replies
    1. Sonjia, You are in Portugal - lucky you - we love Portugal. I believe that the Gulf Stream is lower than usual, so you are experiencing Scottish weather while we are receiving Arctic weather! I think it is set to improve soon. We have had some lovely holidays in the Algarve and that is really where my interest in photographing butterflies started. We would love to see more of Portugal. I found the area away from the built up coast so interesting and unspoilt.

      Delete
  8. Just came back to say that I'm delighted that the Algarve sparked your interest in butterfly photography, and also share your view about the unspoilt countryside.
    We have just returned from Vau in the Algarve, but sadly the weather was poor for this time of year.I hope you're right and the weather improves soon, as where we live, on a farm north of Porto it's been atrocious!

    ReplyDelete
    Replies
    1. A farm north of Porto sounds like paradise (apart from this year's weather!). My wife and I dream of moving to a small farm in Portugal or Spain. Of course if the weather patterns remain like this we will have to consider somewhere further south!!

      Delete
  9. What a pretty butterfly! I love how colourful it is. But I'm sure that seeing that mass of caterpillars moving around can make a gardener's heart stop!

    ReplyDelete
    Replies
    1. Hi Sunita, Luckily they eat nettles, which are not a gardener's friend, so no problem there!

      Delete